Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.90	10.318%	$152.1285	$152.13	$152.15	$152.10
Purchase #2	$72.77	8.518%	$78.9685	$78.97	$78.95	$79.00
Purchase #3	$174.27	10.377%	$192.354	$192.35	$192.35	$192.40
Purchase #4	$219.98	6.147%	$233.5022	$233.50	$233.50	$233.50
Purchase #5	$64.79	11.636%	$72.329	$72.33	$72.35	$72.30
Purchase #6	$179.87	5.731%	$190.1783	$190.18	$190.20	$190.20
Purchase #7	$170.44	3.295%	$176.056	$176.06	$176.05	$176.10
7 purchase totals =	$1,020.02		$1,095.5165	$1,095.52	$1,095.55	$1,095.60